The UN refugee agency expressed sadness on Tuesday after at least five people, including three children, drowned when a small motorized boat sank off the French territory of Mayotte in the Indian Ocean.

Nineteen people were rescued and taken to Mayotte after the vessel foundered on a coral reef Saturday, while another 15 people are missing and feared drowned, according to officials.

“The incident is a further tragic illustration of the dangers faced by people who take desperate measures to escape poverty, conflict and persecution,” a UNHCR spokesman said. “As in the Mediterranean Sea and the Gulf of Aden, the seas around Mayotte are the scene of irregular movements of migrants and refugees searching for a better life or protection from persecution and war,” he added.

The small boat hit coral reefs surrounding a lagoon in Mayotte, a French overseas department. It had set sail from Anjouan Island in the neighbouring archipelago nation of the Comoros.

According to the Mayotte authorities, some survivors were left clinging to the half-sunken vessel overnight. They were located on Sunday morning by a group of divers from a local club, who came to their rescue.

The survivors were suffering from hypothermia and dehydration, and some had fractures and other injuries. The French Ministry of Overseas Territories said the 19 rescued survivors were taken to hospital in Mamoudzou, the capital of Mayotte.

A search and rescue operation, involving navy vessels and aircraft, was launched on Sunday. On Monday, the authorities announced that they were calling off the search, after no more survivors had been found. “UNHCR commends the actions of the local search and rescue authorities and of individuals from a local diving club who came to the rescue of the survivors,” the spokesman said.

For decades, people have been using small open vessels known as kwassa-kwassa to sail from the Comoros to the more prosperous French territory of Mayotte. Many of these movements take place without the documentation and involve considerable risk to those attempting them. Figures for these irregular movements are not available. Asylum seekers account for a small proportion of these movements and their numbers have been increasing in the last two years.

Last year, there were some 1,200 applications for asylum in Mayotte, 41 per cent more than in 2010. The largest proportion came from the Comoros Islands (90 per cent), with citizens from Burundi, the Democratic Republic of the Congo, Madagascar and Rwanda accounting for the rest. Last year some 20,000 people, including failed asylum-seekers, were sent back from Mayotte to the Comoros and Madagascar.

UNHCR assists the local authorities and civil society in France, including its overseas territories, to deal with the challenges posed by mixed flows of irregular migrants and asylum seekers. UNHCR insists that any border controls and measures need to ensure that those who seek protection from persecution and conflict are properly identified and have access to procedures to assess their needs.